Decompression Diving and the Technical Diver

Posted on: July 17, 2012

By Steve Lewis

When the diving community attempts to set a definition for a technique, procedure or even a piece of kit… whoops, sorry I should say equipment… there is seldom complete agreement.

Our community is simply too diverse, too geographically dispersed, too individual to be easily categorized. And as the saying goes: ask a half-dozen divers to define technical diving and you’ll get 12 different answers.

You may have experienced this particular phenomenon for yourself. However, the chances are good that most, if not all, of those definitions will mention something about decompression diving. It is this that truly marks the boundary between sport diving and its young sibling: technical diving.

Somebody once wrote that decompression diving is the art of “staying down longer and coming up slower!” And for most of us, this serves as a workable cocktail party definition.

More precisely, decompression diving (or staged decompression diving since all dives really are decompression dives), exposes a diver to much greater risk than traditional sport dives carried out within the “No Decompression Limits” of his or her chosen Personal Dive Computer (or dive tables). Those increased risks include — in no particular order and not a definitive listing — decompression sickness, running out of gas, getting lost, getting separated from their buddy, getting cold, disorientation attributable to narcosis, lack of situational awareness due to task-loading, and loss of buoyancy control coupled with the potential for run-away ascents and possible embolism. We might also add, either Hypercapnia, Hypoxia, or Hyperoxia resulting in loss of consciousness and death.

Presented with that sobering list of party-poopers, is it any wonder that for the first thirty years of recreational dive instruction, staged decompression diving was not heavily promoted, and certainly was not part of the regular curriculum of any of the mainstream training agencies. If you conducted decompression dives, you were branded by most of the dive community as a foolhardy daredevil with a death-wish; or simply an idiot.

Ironically, when TDI began teaching its original decompression procedures program back in 1994, the concept was so outside the box that several of the long-established training agencies — which had built their reputations entirely on sport-diving certs and by totally ignoring gases other than air, solo diving, deep diving, and decompression diving — suggested that teaching divers deco diving would result in greater instances of DCS, and a rash of diver drownings. “It’s just too complicated'” they crowed.

The facts of course turned out to be somewhat different and according to DAN statistics, the incidents of decompression sickness per 1000 dives has dropped, not increased, since TDI (and a couple of other ground-breakers) started to share the basic skills that are needed to conduct staged decompression dives correctly. Coincidence? Perhaps, but we like to think that by presenting divers with a choice to complete structured training with a qualified and insured and experienced instructor — rather than winging it with advice from cyber-divers — we are making scuba diving a little safer.

Certainly the TDI course has evolved somewhat since it was first introduced. The skills have remained unchanged — with a couple of notable exceptions — but the way we deliver them and the data we have to back-up some of the suggested techniques and procedures have become, forgive the pun, deeper. The simple fact is that 20 years ago, decompression diving was totally behind the curtain, hidden, hardly mentioned; and now it’s mainstream and the experience we have to inform our curriculum and our suggestions is much broader and more comprehensive than it could possibly have been in 1994. Hence, the change and the need for TDI to have a constant process of updating materials (SEE LINK BELOW).

However, as much as TDI’s decompression program has evolved — and even split to include the use of helitrox (light trimix) — many of the basic skills have remained the same.

In some regard, and bringing us full circle, the skills required to conduct staged decompression dives, truly define technical diving and technical divers.

So let’s look briefly at them and let’s find out what benefits they deliver to us as technical divers.

Number one is risk management. This breaks down into risk identification: what can happen; risk assessment: how likely is it to happen; risk analysis: if it happens, what will the consequences be; risk avoidance: how can I arrange things to mitigate or avoid those risks. During this process, we get a pretty clear sense of our personal limits and the limits of our equipment, our experience and our training. This is often a rather humbling exercise, but is always informative. Different instructors use different techniques to teach this set of skills… but it is usually fun!

Second comes an upgrade on the basic skills that we learned as divers from day one: buoyancy, propulsion techniques, and staying in contact with and communications with our buddy or buddies. The obvious fallout from this is that we expend minimum effort moving through the water and don’t waste time and burn ourselves out worrying where the heck our buddy has got to. Bottom line: more fun!

The third set of skills sees us taking a careful look at our kit and selecting the right gear for the job. Taking what’s needed no more, and knowing how to use what we do have with us. At this stage, we also develop some good habits such as pre-dive inspections, critical analysis of kit performance and limits and a bunch of related techniques that help make our diving — I think you may recognize a pattern developing — less stressful and more fun.

Lastly, we begin the practice of real gas management. OOA is no longer an option. We learn to plan the gas volume we need AND we begin to plan to use the right gas for the job. Although gas management is a very simple skill with guidelines that anyone can grasp after a few minutes instruction, it’s amazing to watch the light bulb go on above the heads of even very experienced sport divers who realize that they have been pushing the limit on most of their dives! Now, that’s fun to see!

All tied together in a neat package, the real take-home skills for a technical diving learning staged decompression diving is better dive planning skills and more fun and less stress executing those dives.

Of course, the real story is more involved than all this and for the complete low-down, you should contact your local TDI decompression instructor and get his or her advice and mentoring via a full TDI technical diving program.